Augmented phototransformation of brominated disinfection by-products via surface water introduction during sunlit reclaimed water storage

De-Xiu Wu; Yuan-Chu Qin; Wen-Long Wang; Yan-Lin Chen; Qian-Yuan Wu

doi:10.1016/j.jhazmat.2025.139086

Augmented phototransformation of brominated disinfection by-products via surface water introduction during sunlit reclaimed water storage

J Hazard Mater. 2025 Jun 27:495:139086. doi: 10.1016/j.jhazmat.2025.139086. Online ahead of print.

Authors

De-Xiu Wu¹, Yuan-Chu Qin¹, Wen-Long Wang¹, Yan-Lin Chen¹, Qian-Yuan Wu²

Affiliations

¹ Shenzhen Key Laboratory of Ecological Remediation and Carbon Sequestration, Key Laboratory of Microorganism Application and Risk Control, Ministry of Ecology and Environment, Institute of Environment and Ecology, Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, PR China; Key Laboratory of Microorganism Application and Risk Control of Shenzhen, Guangdong Provincial Engineering Research Center for Urban Water Recycling and Environmental Safety, Institute of Environment and Ecology, Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, PR China.
² Shenzhen Key Laboratory of Ecological Remediation and Carbon Sequestration, Key Laboratory of Microorganism Application and Risk Control, Ministry of Ecology and Environment, Institute of Environment and Ecology, Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, PR China; Key Laboratory of Microorganism Application and Risk Control of Shenzhen, Guangdong Provincial Engineering Research Center for Urban Water Recycling and Environmental Safety, Institute of Environment and Ecology, Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, PR China. Electronic address: wu.qianyuan@sz.tsinghua.edu.cn.

PMID: 40602119
DOI: 10.1016/j.jhazmat.2025.139086

Abstract

Ozonation is widely used for reclaimed water disinfection; however, it inevitably produces harmful brominated disinfection by-products (Br-DBPs). When reclaimed water is replenished into surface water, one of its primary applications, Br-DBPs undergo complex phototransformation due to the interaction between surface water and reclaimed water matrices, which remains poorly understood. This study observed that mixing with surface water significantly enhanced both the photolysis rates of Br-DBPs and the detoxification efficiency of reclaimed water. The photolysis rate of adsorbable organic bromine (AOBr) increased significantly from 0.086 h^-1 to 0.20-0.23 h^-1 when mixed with surface waters (p < 0.001). As a surface water proxy, Suwannee River natural organic matter accelerated the photolysis of three AOBr representatives: 2,5-dibromo-3,6-dihydroxyquinone, 3-bromo-4,5-dihydroxybenzoic acid, and 2-bromo-4-(hydroxymethyl)-6-methoxyphenol. The enhanced photolysis was attributed to DOM* and derivative ¹O₂. High-energy ³DOM* showed a stronger correlation with AOBr photolysis acceleration compared to low-energy ³DOM*. Furthermore, mixing with surface water enhanced the detoxification process, reducing toxicity equivalents from 8.5 to 2.9 mg-phenol/L in reclaimed water alone, and from 6.0 to 2.1 mg-phenol/L in mixed water. These findings suggest that mixing with surface water containing DOM with reactive optical properties is a promising strategy for improving water quality during surface storage.

Keywords: Disinfection by-products; Ozonation; Reclaimed water; Surface water; Toxicity.